@Jason Yes, manual sign in corrects the issue but I was using auto sign in previously. I also have this issue on my chromebook since about a month ago (Asus C302CA, beta channel), but I don't have specific versions for you at the moment.

Having same problem as original posters; just grayed out icon, says I'm signed out. Manual sign in option instead of auto-detect makes it work again, but I'd rather not use this method because of the amount of permissions given ("Checker Plus was granted access to your Google Account"). No offense, I just prefer to avoid that whenever possible! (Btw, how do I know those permissions have been revoked again? Thanks..)

@Krakatum_&nbsp;Issue found!It appears that in Chrome 71 the "Block third-party cookies" option (chrome://settings/content/cookies) is also being applied to extensions.Option 1) Go to Allow section and add this site: mail.google.comOption 2) You can turn off the Block third-party cookies